天线原理介绍-Antenna-Theoryppt课件.ppt

BaseStationAntennasCONFIDENTIAL-ProprietaryInformationAntennaTheoryBasicPrinciplesforDailyApplicationsNovember20041F0(MHz) (Meters) (Inches)30 80 160 280 460 800 960 1700 2000 ¼¼SEARCH3UnderstandingtheMysterious“DB”“dBd” – Signalstrengthrelativetoadipoleinemptyspace“dBi” – Signalstrengthrelativetoanisotropicradiator“dB” – Differencebetweentwosignalstrengths“dBm” – Absolutesignalstrengthrelativeto1milliwatt 1mWatt = 0dBm 1Watt = 30dBm 20Watts = 43dBm“dBc” – Signalstrengthrelativetoasignalofknown strength,inthiscase:thecarriersignal Example:-100dBc=100dBbelowcarriersignal Ifcarrieris100Watt=50dBm -100dBc=-:TheLogarithmicScale10*log10(PowerRatio)4EffectofVSWRVSWRReturnLoss(dB)TransmissionLoss(dB)PowerReflected(%)PowerTrans.(%)¥,theflattertheverticalpatternisandthehighertheantennacoverageor“gain”(cont...)Stacking4dipolesverticallyinlinechangesthepatternshape(squashesthedoughnut),illustratedinthelowersection,ofDipolesVerticalPatternHorizontalPattern4DipolesVerticallyStackedSingleDipoleGENERALSTACKINGRULE:Collinearelements(in-linevertically). Optimumspacing(fornon-electricaltilt),andreduces ?parisonofthepower/fieldcharacteristicsofadeviceundertest(DUT)?Gaincanbeassociatedwithcoveragedistanceand/